With this 11th entry, the popular Cat Who series ( The Cat Who Talked to Ghosts ) begins to flag, its charms growing tatty and listless for even the most steadfast cat-and-mystery lovers. Ex-newspaperman James ``Qwill'' Qwilleran and his Siamese Koko and Yum Yum leave Moose County for the big city Down Below to help old friends save the Casablanca, an aging and elegant apartment building threatened with demolition to make way for profitable development. Qwill decides to spend the winter in the Casablanca to determine if it might make a project for the philanthropic Klingenschoen Fund, which he controls. Ensconced in a 14th-floor penthouse, he discovers that its previous tenant, Dianne Bessinger, head of the group trying to save the building, was an art dealer ostensibly murdered by a jealous protegeok . Qwill also plays Scrabble with the building's owner, the eccentric and reclusive Countess; he teaches the game to Koko, who thereby provides him with clues in his investigation of the murder, which he suspects is tied to attempts against the Casablanca. Braun's latest pleases with its descriptions of gentrification and development, but the book ends abruptly, leaving too many loose ends, and central characters Koko and Yum Yum develop no further at all. (Aug.)